There has been generally known a system for reading mutually complementary memory cell data or memory cell data and reference cell data from two memory cells to paired bit lines, and for detecting/comparing and amplifying a difference between the mutually complementary memory cell data or between the memory cell data and the reference cell data using a sense amplifier in semiconductor storage devices such as a DRAM (Dynamic Random Access Memory), a molecular memory, a NAND flash memory, a NOR flash memory, a PRAM or PCM (Phase-Change Random Access Memory), an iPCM (interfacial PCM), a ReRAM (Resistance Random Access Memory), and an FeRAM (Ferroelectric Random Access Memory), MRAM (Magnetic RAM). In recent years, due to downscaling of memory cells and reduction in power supply voltages, a signal difference between mutually complementary memory cell data or that between memory cell data and reference cell data read from memory cells has become increasingly smaller. When the signal difference between the mutually complementary memory cell data or that between the memory cell data and the reference cell data read from the memory cells is smaller, each sense amplifier possibly erroneously detects/compares and amplifies data logic depending on the irregularity in a threshold voltage between a pair of transistors that constitutes the sense amplifier.